This invention generally relates to vacuum systems and to methods of operating vacuum systems. More specifically, the present invention relates to such systems and methods that are particularly well suited for use in surgical procedures, especially micro surgery, to aspirate the surgical site.
Microsurgical procedures are gaining everincreasing acceptance in the surgical community for preforming precise, minimum invasive surgery for various parts of the body, and one particularly widespread microsurgical application is in the field of ophthalmology.
In this application, commonly, a hand piece having a small tool is used either to cut or to mascerate the eye tissue while an irrigation or infusion liquid is brought to the surgery site. The cut or mascerated tissue is carried away from the surgical site by a suction conduit or tube to a collection vessel such as a bag or bottle. The surgical site may be illuminated by light conducted to that site through an optical fiber.
Consoles are specifically designed for these ophthalmic procedures. These consoles are used to operate the tools and the suction and infusion lines used in the procedures, and to generate the light that is used to illuminate the surgical site. Typically, these consoles have a modular design and include a multitude of separable or removable modules, with each module being used to operate or to perform a specific task. For example, one module may be employed to operate the hand piece used to cut or mascerate the eye tissue, another module may be used to infuse and aspirate the surgical site, and a third module may be used to illuminate that site.
In these procedures, typically, an operator is able to vary the vacuum pressure used to aspirate the surgical site. With one prior art device, for example, this is done by using a diaphragm pump to draw air from a vacuum line, in combination with an adjustable bleed line to bleed air into that vacuum line. More specifically, the pump is operated at a substantially constant speed so that, in the absence of any effect from the bleed line, a substantially constant vacuum pressure would be maintained in the vacuum line. At the same time, a valve in the bleed line is operated, under the control of an operator, to bleed an adjustable amount of air into the vacuum line to vary the pressure therein. For instance, the diaphragm pump may be used to develop a pressure in the vacuum line of 500 mm. of mercury. If the operator wants to increase the pressure in that line, air is bled into the vacuum line until the desired pressure level is reached.
This prior art device is highly effective and reliable. However, the diaphragm pump is some what noisy. In addition, in order to vary the vacuum pressure in the vacuum line over the desired range, a comparatively large valve is required to regulate air flow through the bleed line. Because this valve is large, it is relatively expensive and a comparatively complicated control mechanism is needed to operate the valve.